WO2023031949A1

WO2023031949A1 - A system for controlling compression ratio in a multi-fuel internal combustion engine and a method thereof

Info

Publication number: WO2023031949A1
Application number: PCT/IN2022/050531
Authority: WO
Inventors: Thiruvallur Loganathan BALASUBRAMANIAN; Varadha Iyengar LAKSHMINARASIMHAN
Original assignee: Tvs Motor Company Limited
Priority date: 2021-08-30
Filing date: 2022-06-08
Publication date: 2023-03-09
Also published as: CO2024004027A2

Abstract

The present invention relates to a system (100) for controlling compression ratio of a multi-fuel internal combustion engine and a method (200) thereof, having a control unit (110) and a variable compression ratio mechanism (150). The control unit (110) has a fuel selection module (112) to select between a liquid fuel and a gaseous fuel based on input received from a fuel selection switch (120), a lambda control module (114) to identify the blend ratio of the liquid fuel selected by the fuel selection module (112) based on input received from a fuel sensor (130) and a compression ratio determination module (116) to determine a compression ratio for the selected fuel based on the type of fuel. The variable compression ratio mechanism (150) varies the compression ratio of the internal combustion engine according to the compression ratio determined by the compression ratio determination module (116).

Description

TITLE OF INVENTION

A System for Controlling Compression Ratio in a multi-fuel Internal Combustion Engine and a Method thereof

FIELD OF THE INVENTION

[001 ] The present invention generally relates to an internal combustion engine with variable compression ratio. More particularly, it relates to a system for controlling compression ratio in a multi-fuel internal combustion engine and a method thereof.

BACKGROUND OF THE INVENTION

[002] Generally, automobile engines are designed to work on a specific type of fuel. Such engines operate at their maximum efficiency when the fuel used has the exact characteristics suitable for that particular engine design. When a fuel with different properties is used either the efficiency of the engine drops or the engine breaks down. Variations in the characteristics of the fuel used for combustion can potentially cause damage to the engine and the powertrain.

[003] New fuels and fuel compositions have been developed to achieve specific needs of a user. For example, alternate fuels like Ethanol, Methanol, CNG, etc. which have higher octane numbers can be used at higher compression ratios and have a lesser impact on the environment. Sometimes fuel admixtures are used like a mixture of petrol and ethanol in varying ratios. Such alternate fuels can achieve a higher fuel economy and emission benefits if engines are specifically designed for the given fuel. However, designing engines to work on only a single alternate fuel limits its applicability and versatility, especially in areas where the use of a different alternate fuel is prevalent. [004] With the increase in bi-fuel engines which are capable of using both a liquid fuel and a gaseous fuel, variable compression ratio engines have become more prevalent. A variable compression ratio engine needs to be configured to function on compression ratios suitable for the liquid fuel as well as the gaseous fuel. To achieve maximum efficiency, it is desirable to determine the compression ratio of such a variable compression ratio engine based on the type of fuel used. Conventionally used variable compression ratio mechanisms vary the compression ratio of the engine based on certain conditionalities like providing higher compression ratio at part load and lower compression ratio at full load, or higher compression ratio for increasing combustion efficiency and lower compression ratio for avoiding knocking. [005] Thus, there is a need in the art for a system and method for controlling compression ratio of a multi-fuel internal combustion engine which addresses at least the aforementioned problems.

SUMMARY OF THE INVENTION

[006] In one aspect, the present invention is directed to a system for controlling compression ratio of a multi-fuel internal combustion engine, having a control unit and a variable compression ratio mechanism. The control unit has a fuel selection module, a lambda control module and a compression ratio determination module. The fuel selection module selects between a liquid fuel and a gaseous fuel based on input received from a fuel selection switch. The lambda control module identifies the blend ratio of the liquid fuel selected by the fuel selection module based on input received from a fuel sensor. The compression ratio determination module determines a compression ratio for the selected liquid fuel based on the type of liquid fuel and the blend ratio, or for the selected gaseous fuel based on the type of gaseous fuel. The variable compression ratio mechanism varies the compression ratio of the internal combustion engine according to the compression ratio determined by the compression ratio determination module.

[007] In another embodiment, the variable compression ratio mechanism of the internal combustion engine is actuated by a controller.

[008] In a further embodiment, the control unit of the system for controlling compression ratio of a multi-fuel internal combustion engine actuates the variable compression ratio mechanism of the internal combustion engine.

[009] In a further embodiment, the compression ratio determination module determines a specific first compression ratio when the fuel selected by the fuel selection module is a gaseous fuel.

[010] In a further embodiment, the compression ratio determination module determines a specific second compression ratio when the fuel selected by the fuel selection module is a liquid fuel and the blend ratio of the liquid fuel is lower than a predetermined blend ratio. The compression ratio determination module determines a specific third compression ratio when the fuel selected by the fuel selection module is a liquid fuel and the blend ratio of the liquid fuel is higher than a predetermined blend ratio.

[011] In a further embodiment, the variable compression ratio mechanism has a variable compression ratio shaft and a variable compression ratio actuator. The variable compression ratio shaft which is connected to a connecting rod of a piston and a crankshaft is actuated by the variable compression ratio actuator for controlling the compression ratio of the engine. [012] In another aspect, the present invention is directed to a method for controlling compression ratio in a multi-fuel internal combustion engine. The method includes the steps of selecting between a liquid fuel and a gaseous fuel, identifying the blend ratio if a liquid fuel is selected, determining the compression ratio for the selected fuel and varying the compression ratio of the internal combustion engine accordingly.

[013] In yet another embodiment, the method includes the determination of a specific first compression ratio by the compression ratio determination module when the fuel selected by the fuel selection module is a gaseous fuel, wherein the first compression ratio ranges from

13.5 to 16.

[014] In yet another embodiment, the method includes the determination of a specific second compression ratio or a specific third compression ratio by the compression ratio determination module when the fuel selected by the fuel selection module is a liquid fuel, wherein the predetermined blend ratio ranges from 0.2 to 0.4.

[015] In yet another embodiment, the method includes the determination of the specific second compression ratio by the compression ratio determination module when the fuel selected by the fuel selection module is a liquid fuel and the blend ratio of the liquid fuel is lower than a predetermined blend ratio, wherein the second compression ratio ranges from

9.5 to 11.

[016] In yet another embodiment, the method includes the determination of the specific third compression ratio by the compression ratio determination module when the fuel selected by the fuel selection module is a liquid fuel and the blend ratio of the liquid fuel is higher than a predetermined blend ratio, wherein the third compression ratio ranges from 10.5 to 13. BRIEF DESCRIPTION OF THE DRAWINGS

[017] Reference will be made to embodiments of the invention, examples of which may be illustrated in accompanying figures. These figures are intended to be illustrative, not limiting. Although the invention is generally described in context of these embodiments, it should be understood that it is not intended to limit the scope of the invention to these particular embodiments.

Figure 1 illustrates a right side view of an exemplary motor vehicle, in accordance with an embodiment of the present invention.

Figure 2 illustrates a schematic block diagram of a system for controlling compression ratio in a multi-fuel internal combustion engine, in accordance with an embodiment of the present invention.

Figure 3 illustrates a cross sectional view of the internal combustion engine with the variable compression ratio mechanism, in accordance with an embodiment of the present invention.

Figure 4 illustrates a method flowchart of controlling the compression ratio in a multifuel internal combustion engine, in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[018] The present invention generally relates to an internal combustion engine with variable compression ratio. More particularly, the present invention relates to a system for controlling compression ratio in a multi-fuel internal combustion engine and a method thereof.

[019] Figure 1 illustrates an exemplary motor vehicle 10, in accordance with an embodiment of the invention. The motor vehicle 10 includes an internal combustion engine 12 that is vertically disposed. Preferably, the Internal combustion engine 12 is a single-cylinder type internal combustion engine. The motor vehicle 10 further includes a front wheel 14, a rear wheel 16, a frame member, a seat assembly 18 and a fuel tank 44. The frame member includes a head pipe 22, a main tube 24, a down tube (not shown), and seat rails (not shown). The head pipe 22 supports a steering shaft (not shown) and two telescopic front suspensions 26 (only one shown) attached to the steering shaft through a lower bracket (not shown). The two telescopic front suspensions 26 support the front wheel 14. The upper portion of the front wheel 14 is covered by a front fender 28 mounted to the lower portion of the telescopic front suspension 26 at the end of the steering shaft. A head light 32, a visor guard (not shown) and instrument cluster (not shown) are arranged on an upper portion of the head pipe 22. The frame member having the down tube (not shown) may be located in front of the internal combustion engine 12 and extends slantly downward from the head pipe 22. The main tube 24 of the frame member is located above the internal combustion engine 12 and extends rearward from the head pipe 22. The internal combustion engine 12 is mounted at the front to the down tube and a rear of the Internal combustion engine 12 is mounted at the rear portion of the main tube 24. In an embodiment, the internal combustion engine 12 is mounted vertically, with a cylinder block extending vertically above a crankcase. In an alternative embodiment, the Internal combustion engine 12 is mounted horizontally (not shown) with the cylinder block extending horizontally forwardly from the crankcase. In an embodiment, the cylinder block is disposed rearwardly of the down tube.

[020] The fuel tank 44 of the motor vehicle 10 is mounted on the horizontal portion of the main tube 24. Seat rails are joined to the main tube 24 and extend rearward to support the seat assembly 18. A rear swing arm 34 is connected to the frame member to swing vertically, and the rear wheel 16 is connected to rear end of the rear swing arm 34. Generally, the rear swing arm 34 is supported by a mono rear suspension 36 or through two suspensions on either side of the motor vehicle 10. A taillight unit 33 is disposed at the end of the motor vehicle 10 and at the rear of the seat assembly 18. A grab rail 35 is also provided on the rear of the seat rails. The rear wheel 16 arranged below seat 18 rotates by the driving force of the Internal combustion engine 12 transmitted through a chain drive (not shown) from the Internal combustion engine 12. A rear fender 38 is disposed above the rear wheel 16.

[021 ] Further, an exhaust pipe 40 of the motor vehicle 10 extends vertically downward from the Internal combustion engine 12 up to a point and then extends below the Internal combustion engine 12, longitudinally along the vehicle length before terminating in a muffler 42. The muffler 42 is typically disposed adjoining the rear wheel 16.

[022] The vehicle 10 further includes a handlebar 30 connected to the head tube 22 of the frame member and extending in a vehicle width direction (W) (shown in Figure 4). The handlebar 30 can rotate to both sides of the vehicle 10 during vehicle turning movements.

[023] Figure 2 illustrates a schematic block diagram of a system 100 for controlling compression ratio in a multi-fuel internal combustion engine 12, in accordance with an embodiment of the invention. The internal combustion engine 12 of the saddle type vehicle is a multi-fuel engine that is configured to run on a plurality of liquid and gaseous fuels as per requirement. The system 100 for controlling the compression ratio comprises a control unit 110 having a fuel selection module 112, a lambda control module 114 and a compression ratio determination module 116. The fuel selection module 112 is configured to select between a liquid fuel and a gaseous fuel based on input received from a fuel selection switch 120. The fuel selection switch 120 is operated by the user to select the type of fuel to used at a particular instance. The fuel selection module 112, on selection between the liquid and the gaseous fuel, communicates the same to the lambda control module 114 and/or the compression ratio determination module 116.

[024] Further, the lambda control module 114 is configured to identify the blend ratio of the liquid fuel selected by the fuel selection module based on input received from a fuel sensor 130. Blend ratio is defined as the ratio of volume of an additive to volume of the unblended fuel being used for blending. The lambda control module 114 identifies the blend ratio of the liquid fuel only when the liquid fuel has been selected by the fuel selection module 112. In an embodiment, the fuel sensor 130 is fuel sensing module of the control unit 110. The fuel sensing module receives input from the fuel selection switch and solenoids and actuators placed in the fuel intake manifold.

[025] In an embodiment, the lambda control module 114 is in communication with a plurality of lambda sensors placed in the exhaust of the vehicle. The lambda control module 114 validates a predetermined lambda values for a specified liquid fuel. With the predetermined lambda values for a specified liquid fuel as reference, the lambda control module 114 iteratively determines the blend ratio. The lambda control module 114 then communicates the determined blend ratio to the compression ration determination module 116.

[026] Further, the compression ratio determination module 116 is configured to determine a compression ratio for the selected liquid fuel based on the type of liquid fuel and its blend ratio. In that, the compression ratio determination module 116, in case of the liquid fuels, is configured to determine whether the blend ratio of the liquid fuel identified by the lambda control module 114, greater or lower than a predetermined blend ratio. Additionally, the compression ratio determination module 116 determines a compression ratio for the selected gaseous fuel based on the type of gaseous fuel.

[027] The compression ratio determination module 116 is configured to determine the compression ratio as a first compression ratio when the gaseous fuel is selected by the fuel selection module 112. Further, the compression ratio determination module 116 is configured to determine the compression ratio as a second compression ratio when the liquid fuel is selected by the fuel selection module 112, and the blend ratio of the liquid fuel is lower than a predetermined blend ratio. The compression ratio determination module 116 is further configured to determine the compression ratio as a third compression ratio when the liquid fuel is selected by the fuel selection module 112, and the blend ratio of the liquid fuel is higher than a predetermined blend ratio

[028] The system 100 for controlling the compression ratio further comprises a variable compression ratio mechanism 150. The variable compression ratio mechanism 150 varies the compression ratio of the internal combustion engine according to the compression ratio determined by the compression ratio determination module 116.

[029] In an embodiment, the system 100 for controlling the compression ratio further comprises a controller 140, which is in communication with the control unit 110 and is configured for actuating the variable compression ratio mechanism 150 of the multi-fuel internal combustion engine 12. The controller 140 actuates the variable compression ratio mechanism 150 based on an input received from the compression ratio determination module 116.

[030] Figure 3 illustrates a sectional view of the internal combustion engine 12 with the variable compression ratio mechanism 150, in accordance with an embodiment of the present invention. The variable compression ratio mechanism 150 comprises of a variable compression ratio shaft 152. The variable compression ratio shaft 152 is connected to a connecting rod of a piston and a crankshaft. Different compression ratios for the multi-fuel internal combustion engine 12 are attained by adjusting the position of the variable compression ratio shaft 152.

[031] In an embodiment, the variable compression ratio mechanism 150 comprises of a selector disc (not shown) which is coupled to the variable compression ratio shaft 152. Rotating the selector disc adjusts the position of the variable compression ratio shaft 152, thereby changing the compression ratio for the multi-fuel internal combustion engine 12.

[032] In another embodiment, the variable compression ratio mechanism 150 comprises of a variable compression ratio actuator 154. The variable compression ratio actuator 154 is coupled to the variable compression ratio shaft 152. The variable compression ratio actuator 154 actuates the variable compression ratio shaft 152 based on information received from the controller 140, thereby controlling the compression ratio for the multi-fuel internal combustion engine 12.

[033] Figure 4 illustrates a flowchart for a method 200 of controlling the compression ratio in a multi-fuel internal combustion engine 12, in accordance with an embodiment of the present invention.

[034] At step 2A, input from a fuel selection switch 120 is received by a fuel selection module 112 of a control unit 110. At a step 2B, the fuel selection module 112 determines whether the fuel used is a liquid fuel or a gaseous fuel based on at least an input received from the fuel selection switch 120. Accordingly, the fuel selection module 112 selects between a liquid fuel and a gaseous fuel based on the aforementioned determination. [035] In an embodiment, if the fuel selection module 112 determines that a gaseous fuel is selected, the method 200 moves to step 2EA, and if a liquid fuel is selected by the fuel selection module 112, the method 200 moves to step 2C. At step 2EA, the compression ratio determination module 116 determines a first compression ratio when the fuel selected by the fuel selection module 112 is a gaseous fuel, after which the method 200 moves to step 2F.

[036] At a step 2C, input from a fuel sensor 130 is received by a lambda control module 114 of the control unit 110 when the fuel selected by the fuel selection module 112 is a liquid fuel. The lambda control module 114 determines the blend ratio of the liquid fuel selected by the fuel selection module 112. At a step 2D of the method 200, the blend ratio of the liquid fuel determined by the lambda control module 114 is compared with a predetermined value of blend ratio. In an embodiment, the predetermined blend ratio ranges between 0.2 and 0.4.

[037] In an embodiment, at step 2EB of the method 200, the compression ratio determination module 116 of the system 100 determines a second compression ratio when the blend ratio of the liquid fuel determined by the lambda control module 114 is lower than a predetermined value of blend ratio, after which the method 200 moves to step 2F.

[038] At step 2EC, the compression ratio determination module 116 of the system 100 determines a third compression ratio when the blend ratio of the liquid fuel determined by the lambda control module 114 is higher than a predetermined value of blend ratio. Consequently, at step 2F of the method 200, the variable compression ratio mechanism 150 is actuated by the controller 140, thereby setting the compression ratio for the multi-fuel internal combustion engine 12 as the first compression ratio, the second compression ratio or the third compression ratio as required. [039] In an embodiment, when the fuel selected by the fuel selection module 112 is a gaseous fuel, the first compression ratio ranges from 13.5 to 16. In another embodiment, when the liquid fuel is selected by the fuel selection module, the second compression ratio ranges between 9.5 to 11 , and the third compression ratio ranges between 10.5 to 13.

[040] Advantageously, the present invention provides a system and method for controlling compression ratio in a multi-fuel internal combustion engine that can control the compression ratio of an engine based on the type of fuel used, thereby achieving required compression ratio for a gaseous fuel, and required compression ratio for a liquid fuel based on the blend ratio of the specific liquid fuel. This allows for the use of different fuels in the same engine, each at the engine’s optimum efficiency. It also allows for the optimal use of different blends of fuels in the engine. Such use of different fuels in the engine at the desirable compression ratio of each fuel type helps in avoiding damage to engine and powertrain components. Moreover, this system and method enables the engine to achieve its best thermal performance for any type of fuel used.

[041 ] While the present invention has been described with respect to certain embodiments, it will be apparent to those skilled in the art that various changes and modification may be made without departing from the scope of the invention as defined in the following claims.

Claims

CLAIMS:

1 . A system (100) for controlling compression ratio in a multi-fuel internal combustion engine (12), comprising: a control unit (110) having: a fuel selection module (112) configured for selecting between a liquid fuel and a gaseous fuel based on at least an input received from a fuel selection switch (120); a lambda control module (114) configured for identifying blend ratio of the liquid fuel selected by the fuel selection module (112) based on at least an input received from a fuel sensor (130); and a compression ratio determination module (116) configured for determining a compression ratio for the selected liquid fuel based on the type of liquid fuel and the blend ratio, or for the selected gaseous fuel based on the type of gaseous fuel; and a variable compression ratio mechanism (150) configured to vary the compression ratio of the internal combustion engine (12) based on at least the determined compression ratio by the compression ratio determination module (116).

2. The system (100) as claimed in claim 1 , comprising a controller (140) configured for actuating the variable compression ratio mechanism (150) of the internal combustion engine (12).

3. The system as claimed in claim 1 , wherein the control unit (110) is configured for actuating the variable compression ratio mechanism (150) of the internal combustion engine (12).

4. The system (100) as claimed in claim 1 , wherein the compression ratio determination module (116) is configured to determine the compression ratio as a first compression ratio when the gaseous fuel is selected by the fuel selection module (112).

5. The system (100) as claimed in claim 1 , wherein the compression ratio determination module (116) is configured to determine the compression ratio as a second compression ratio when the liquid fuel is selected by the fuel selection module (112), and the blend ratio of the liquid fuel is lower than a predetermined blend ratio.

6. The system (100) as claimed in claim 1 , wherein the compression ratio determination module (116) is configured to determine the compression ratio as a third compression ratio when the liquid fuel is selected by the fuel selection module (112), and the blend ratio of the liquid fuel is higher than a predetermined blend ratio.

7. The system as claimed in claim 1 , wherein the variable compression ratio mechanism (150) comprises of a variable compression ratio shaft (152) connected to a connecting rod of a piston and a crankshaft, and a variable compression ratio actuator (154) to actuate the variable compression ratio shaft, thereby controlling the compression ratio. 15 A method (200) for controlling compression ratio in a multi-fuel internal combustion engine (12), comprising the steps of: selecting, by a fuel selection module (112) of a control unit (110), between a liquid fuel and a gaseous fuel based on at least an input received from a fuel selection switch (120); identifying, by a lambda control module (114) of the control unit (110), blend ratio of the liquid fuel selected by the fuel selection module (112) based on at least an input received from a fuel sensor (130); determining, by a compression ratio determination module (116) of the control unit (110), a compression ratio for the selected liquid fuel based on the type of liquid fuel and the blend ratio, or for selected the gaseous fuel based on the type of gaseous fuel; and varying, by a variable compression ratio mechanism (150), the compression ratio of the internal combustion engine (12) based on at least the determined compression ratio by the compression ratio determination module (116). The method (200) as claimed in claim 8, wherein a first compression ratio is determined as the compression ratio when the gaseous fuel is selected by the fuel selection module (112). The method (200) as claimed in claim 9, wherein the first compression ratio ranges between 13.5 to 16. The method (200) as claimed in claim 8, wherein a second compression ratio is determined the compression ratio when the liquid fuel is selected by the fuel selection 16 module (112) and the blend ratio of the liquid fuel is lower than the predetermined blend ratio. The method (200) as claimed in claim 8, wherein a third compression ratio is determined as the compression ratio when the liquid fuel is selected by the fuel selection module (112) and the blend ratio of the liquid fuel is higher than the predetermined blend ratio. The method (200) as claimed in claims 11 and 12, wherein the predetermined blend ratio ranges between 0.2 to 0.4. The method (200) as claimed in claim 11 , wherein the second compression ratio ranges between 9.5 to 11. The method (200) as claimed in claim 12, wherein the third compression ratio ranges between 10.5 to 13.